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- 2018 CX-5 GT
The end of Nov 2021, my trusty 2014 Mazda6 got rear-ended and was deemed a total loss by my insurance company, Metromile. They are one of a select few companies that charge based on usage (i.e. mileage), using a small tracking device that ordinarily plugs into the ODBII port on the car. It worked fine on my Mazda6, but it was not to be on the CPO 2018 CX-5 GT that I purchased as my replacement. Several weeks after owning the CX-5 (mid-December, as it got colder), my battery needed a jumpstart, so I took it back to my Mazda dealer and they replaced the 3+ year original battery with a new one. A week or two later, the new battery needed a jumpstart, and so the adventure began. Because the dealer had no loaner cars to give me while they would diagnose and fixed the issue, I took daily voltage and temperature readings, while using the car sporadically, sometimes letting it sit for 2-3 days. On those occasions, the battery voltage would drop below 3.5v and would need a jumpstart. Finally, off to the dealer it went on a flatbed tow truck. They went straight to replacing the power liftgate module, which had a battery drain issue on the 2019/2020 CX-5s, but also removed the Metromile device from the ODBII port. After a week, they informed me that the car was starting fine, and that it was the Metromile device causing the problem. I pushed back, since nothing official in the Mazda documentation warned against such a device, and Metromile bases their entire business on it. Metromile did however have an alternative approach which is an adapter that plugs into the cigarette lighter (in the dashboard) which powers the device only when the car is running. The dealer agreed to plug the device back into my CX-5 over the weekend, and sure enough, the battery was dead after a cold weekend. The service manager insisted that nothing should be plugged into the ODBII port on these newer cars while the engine is not running, because the processors in the various subsystems (e.g. ECM) will not go into "sleep" mode while an active device (e.g. diagnostic scanner) is plugged in. While the device itself draws as low as 10 mA, the car processors, while awake, can draw as much as 500 mA, which will progressively, and more quickly, drain the battery, and much quicker as the temperature drops. All of this could have been avoided if Mazda had put a simple printed tape across the ODBII port warning not to plug into the port when the car if not running. Since switching to the alternative Metromile adapter, I have left my car for 7-10 days and it started, as it should, without a hitch.
I hope my weeks of grief and frustration documented here will help anyone struggling with the same puzzlement.
I hope my weeks of grief and frustration documented here will help anyone struggling with the same puzzlement.